The long-term goal of these studies is to explore the utility of silver carbene complexes as antimicrobial agents in the treatment of pulmonary infections with emphasis on treatment of the chronic infections of the cystic fibrosis (CF) lung. Silver N-heterocyclic carbene complexes have antimicrobial activity against all bacterial species tested to date including the CF lung pathogens Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc) organisms. The silver carbene complexes are water soluble, and hence amenable to nebulization for drug delivery. Silver complexes have a long history of safe use for topical applications, however, the use of silver compounds to treat pulmonary infections has not been explored. In addition to in vitro and in vivo toxicity studies aimed at determining the effects of silver complexes on the respiratory epithelium, we will establish the efficacy of these compounds for treatment of the primary CF pathogen P. aeruginosa, as well as the less common Bcc organisms, particularly B. dolosa, the causative agent of a recent epidemic. The B. dolosa strains are the most antibiotic resistant among the Bcc organisms. Virtually nothing is known about the pathogenesis of the lung infections caused by B. dolosa, and no effective therapy currently exists for these patients. We aim to characterize a novel murine model of 8. dolosa infection and use this model, as well as more established models of P. aeruginosa lung infections, to test the in vivo properties of these newly developed silver-based antimicrobial agents. Specifically, we aim to 1) synthesize silver carbene complexes as candidate antimicrobial agents; 2) determine the antimicrobial properties and toxicity profiles of the silver carbene compounds with the most promising physical properties, as well as the mechanisms of epithelial cell-silver toxicity or detoxification; and 3) develop murine models of chronic pulmonary infection with resistant CF pathogens and use these models to determine the in vivo efficacy of the leading silver carbene compounds for treatment of pulmonary infections.